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US 6,185,300 B2Granted
Echo canceler for use in communications system
AssigneeEricsson Inc.
InventorEric Douglas Romesburg
Life of this patent
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AssigneeEricsson Inc.
InventorEric Douglas Romesburg
Estimating the term…
An echo canceler in which effective transfer function coefficients of an adaptive echo-canceling filter are adjusted periodically to track changing system conditions. Periodic adjustment of the effective coefficients is accomplished using a set of more frequently adjusted update coefficients and an update gain which is varied based on a strategic and novel combination of system parameter measurements. By updating filtering coefficients periodically rather than continuously, and by making soft, fuzzy-logic-type decisions with respect to the magnitude of the update gain, exemplary embodiments optimize system speed and adaptability without sacrificing stability. Generally, relatively large update gains are applied in situations where only a far-end user is speaking and a near-end signal is relatively noise-free. However, in near-end single talk, double-talk, and high near-end noise situations, a more conservative approach is used so that the adaptive filter does not become unstable or cause distortion in the near-end speech and noise signals. In either event, the update gain is reduced as the adaptive filter converges to match a prevailing steady-state echo environment so that erroneous perturbations of an already properly-adapted filter are minimized. The decision as to whether to apply high or low update gains during periods of nonconvergence is based in part on a system status gauge comprising a ratio of a peak update coefficient value and a baseline update coefficient value. The system status gauge indicates, among other things, a level of system convergence. In exemplary embodiments, relatively high variable update gains are applied in unconverged, far-end single-talk situations by employing a modified normalized least-mean-squares (NLMS) algorithm.
An echo canceling device for estimating an echo component of an input signal and for subtracting a resulting echo component estimate from the input signal to provide an echo-canceled output signal, wherein the echo component of the input signal results from an echo-causing signal, the echo canceling device comprising:
A method for canceling an echo component of an input signal, wherein the echo component of the input signal results from an echo-causing signal, comprising the steps of:
An echo canceling device for estimating an echo component of an input signal and for subtracting a resulting echo component estimate from the input signal to provide an echo-canceled output signal, wherein the echo component of the input signal results from an echo-causing signal, the echo canceling device comprising:
An echo canceling device for estimating an echo component of an input signal and for subtracting a resulting echo component estimate from the input signal to provide an echo-canceled output signal, wherein the echo component of the input signal results from an echo-causing signal, the echo canceling device comprising:
A method for canceling an echo component of an input signal, wherein the echo component of the input signal results from an echo-causing signal, comprising the steps of:
An echo canceling device for estimating an echo component of an input signal and for subtracting a resulting echo component estimate from the input signal to provide an echo-canceled output signal, wherein the echo component of the input signal results from an echo-causing signal, the echo canceling device comprising:
Dependencies are inferred from the claim text.